1. Field of the Invention
The present invention relates to a pressure control system, especially for a pressure control system of a wafer polishing apparatus.
2. Description of Related Art
As shown in FIG. 1, a traditional pressure control system for a wafer polishing apparatus includes a main input air pressure regulator 1a, an air branch conduit 2a, a plurality of air pipes 3a, and a plurality of air pressure controlling devices 4a. The air branch conduit 2a is connected to the main input air pressure regulator 1a. Each of the air pipes 3a is connected to the air branch conduit 2a on one end and, while another end thereof has a plurality of branches 31a connected to the air pressure controlling devices 4a respectively, which are for controlling the pressure outputted from a polishing head of the wafer polishing apparatus to a wafer.
In order to ensure the application of sufficient pressure from the polishing heads to the wafer, ideally the pressure value inputted to each of the air pressure controlling devices 4a should be maintained at around 25 psi, so that the quality of wafer polishing can be ensured. However, in reality, because the branches 31a are in connection with each other, fluctuation of air pressure in these air pressure controlling devices 4a frequently occurs. As a result, the pressure value in some of these controlling devices are higher than 25 psi, while others are lower than 25 psi. Moreover, when the pressure value of the air pressure controlling device 4a is lower than 25 psi, the polishing head may not be able to apply sufficient output pressure to keep the spinning wafer on the pad of the polishing apparatus. In extreme situations, the wafer may even be thrown off the pad of the polishing apparatus. However, when the pressure value of the air pressure controlling device 4a is higher than 30 psi to exceed the rated pressure of the air pressure controlling device 4a, the air pressure controlling devices 4a is damaged and the life of the air pressure controlling device 4a is reduced.
Hence, the inventors of the present invention believe that the shortcomings described above are able to be improved and finally suggest the present invention which is of a reasonable design and is an effective improvement based on deep research and thought.